Scr catalytic system

Abstract

According to the present disclosure, there is provided an SCR catalytic system including an SCR catalyst that absorbs NH 3 and reduces NOx using the absorbed NH 3 as a reducing agent. In the SCR catalytic system, the SCR catalyst is a Cu- and Mg-containing CHA zeolite in which a silica-alumina ratio (SiO 2 /Al 2 O 3 molar ratio) is 10 to 13 and 0.18 weight % to 0.44 weight % of Mg is contained.

What is claimed is: 
     
         1 . An SCR catalytic system comprising:
 an SCR catalyst which is a Cu- and Mg-containing CHA zeolite in which a molar ratio of SiO 2  with respect to Al 2 O 3  is 10 to 13 and 0.18 weight % to 0.44 weight % of Mg is contained, and which absorbs NH 3  and reduces NOx using the absorbed NH 3  as a reducing agent.   
     
     
         2 . The SCR catalytic system according to  claim 1 , wherein NH 3  generated when fuel is temporarily injected into an engine such that a combustion state of the engine becomes a rich state is used as a reducing agent of the SCR catalyst.